Process of making polypropylene from intermediate grade propylene

Abstract

This invention concerns using an intermediate grade propylene stream as feed to a polypropylene forming reaction system. The intermediate grade propylene stream is preferably recovered form the olefin product of an oxygenate to olefins reaction process, and low in dimethyl ether content.

Description

FIELD OF THE INVENTION [0001] This invention concerns polypropylene manufacturing processes. In particular, this invention concerns processes of making polypropylene from intermediate grade propylene. BACKGROUND OF THE INVENTION [0002] Polypropylene reaction processes involve adding propylene, a polypropylene forming catalyst, and other optional compounds, to a polymer reactor and producing polypropylene product. The product emerging from the reactor contains various contaminants, including unreacted propylene, that must be removed in order to obtain an acceptable polymer. [0003] Propylene feedstreams for the production of polypropylene, as well as for the production of numerous other products, have traditionally been obtained through cracking of hydrocarbons. Non-catalytic cracking processes are described, for example, in Hallee et al., U.S. Pat. No. 3,407,789; Woebcke, U.S. Pat. No. 3,820,955, DiNicolantonio, U.S. Pat. No. 4,499,055 and Gartside et al., U.S. Pat. No. 4,814,067. Ca...

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Benefits of technology

[0012] In a preferred embodiment, the intermediate grade propylene stream of the invention contains less than 99 wt % propylene, based on total weight of the stream. More preferably, the intermediate grade propylene stream co

Problems solved by technology

This patent further notes that the presence of propane is typically a problem in polypropylene reaction systems, and the removal of propane is particularly difficult.

The difficulty in removing propane from propylene streams means that extensive separation equipment is required to obtain a polymer grade propylene feedstream.

In turn, such equipment is expensive and substantially increases the cost of the polymer grade propylene feedstream.

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